Edwin Pawlowski wrote:

Their idea can work. It may feel crumbly on top, but you still have a 4'
deep solid mass. Get more details as to exactly what they will do. I would
think they'd want to dig down at least a few inches and pour a ring at least
a few inches wider than the existing piers. See if you can get some
guarantee against frost heaves due to the original improper installation.

You may also want to post this on alt.home.repair for more information.
Ed

But what if the concrete was indeed mixed incorrectly? IMO, it will be
crumbly

for the entire 4' length through the ground. It won't be a solid
supporting mass at all.

I'm sure the concrete below the patch will deteriorate also. A fix? New
posts in new concrete...
Mark L.